Epinephrine contribution to leptin level regulation during a 4-hour treadmill exercise

In a previous study (Zaccaria et al.,E ur J Appl Physiol 2002; 87: 108–112), we found that prolonged exercises,diff ering in intensity and duration,induce a decrease in leptin levels,and that this effect appears proportional to their energy expenditure, but the mechanisms involved in this reduction are still unclear. It is well known that catecholamines strongly increase during prolonged exercise, and recent research demonstrated their ability to suppress leptin secretion both in vitro and in vivo conditions. The aim of our study was to verify if catecholamines may contribute to leptin decrease during and after an endurance exercise. Seven male athletes (age 27±4.2 y,mean ± SD) performed a four-hour treadmill exercise. Both speed and incline were modified to maintain lactate levels between 1.5–2.0 mM/L and an exercise intensity of about 60% of VO2 max. A 10-minute sample of expiratory gas exchanges and blood samples for leptin (Lep), epinephrine (E) and norepinephrine (NE), were collected, in post-absorptive conditions, at rest, and each hour during the exercise. Results are expressed as mean ± SE. Total energy expenditure, calculated from gas analysis data,was 3364±96 kcal. Lep remained unchanged until 180 min and then showed a slight but significant decrease (from 1.103±0.388 at rest, to 0.846±0.246 mg/L at 240 min,p <0.005) of about 19% at the end of the exercise. On the other hand, both E and NE significantly increased during exercise (from 48.1±30.3 to 352.3±187.7 at 240min and from 238.1±118.9 to 1798.7±413.5 at 240 min, respectively), reaching a peak after 180min. Moreover, leptin levels showed a significant inverse relationship with E (r=–0.459, p<0.015),while NE did not. Our data suggest that epinephrine may contribute to leptin suppression observed during acute, prolonged exercise.